Optimizing operational requests of logical volumes

ABSTRACT

A method, system, apparatus and computer program product for determining an optimal file operational time in a data storage system for use with a tape media storing data in a serpentine pattern on tape media is provided. The operational time is optimized based on a “sequence on tape” algorithm, a “minimum reversal of direction on tape” algorithm, or a “minimum delay to next data” algorithm. A model is used to determine the predicted performance of each of the algorithms, and the algorithm that provides the minimum overall operational time is chosen and applied for carrying out an operational process on the tape media.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to operations on logical volumes in a virtualtape server and more particularly to optimizing operational requests onlogical volumes using algorithms.

2. Description of the Related Art

Data Processing systems typically require large amounts of data storagecapacity. Portions of the data storage capacity may be needed quicklyand may be stored in memory and hard disk drives. Other portions of thedata storage capacity may not be required immediately.

As an example, data not immediately required may comprise data that isinfrequently accessed. Storage of such data may be in the form oflogical volumes of data stored on removable re-writable physical mediavolumes, such as magnetic tape or optical disk, and the physical mediavolumes may be written and/or read by means of a data storage drive.

If large amounts of data are to be stored and then accessed on occasion,virtual tape servers (VTS) backed by automated data storage librariesare often employed. Such libraries provide efficient access to largequantities of data stored on physical media volumes which are stored instorage shelves, accessed by one or more users and delivered to datastorage drives in the library.

A request by a host data processing system to create or modify a logicalvolume is issued to a VTS. If the request requires access to a physicalmedia volume that contains the requested logical volume, the VTSinstructs its attached library to access the physical media volume fromthe storage shelf and mount the physical media volume at a desired datastorage drive. The logical volume is read to cache storage, which maycomprise hard disk drives or other high-speed storage, so that it may beimmediately accessed and provided to the host system.

If the request is for a logical volume that is already in cache, or isfor a logical volume that will be completely rewritten, a physical mediavolume access is not required. The host system then reads from or writesto the logical volume in the cache of the VTS. When the logical volumeis closed, it remains in cache storage so that it can be immediatelyre-accessed.

The cache storage is typically limited in capacity, requiring that theupdated logical volumes be migrated back in storage so as to free spacein the cache storage. Typically a least recently used (LRU) algorithm isemployed to migrate logical volumes out of cache storage back tophysical media.

Recalling and copying a migrated logical volume requires that thephysical media volume containing the migrated logical volume be mountedon a data storage drive. This allows the logical volume to be recalledinto cache storage, re-accessed and copied.

Volume mapping is used to create a correlation between the physicalcapacity of a storage cartridge (stacked volume or physical volume) andthe data storage unit size (virtual volumes or logical volumes) of afile or block that is stored on the cartridge. Given the available datastorage capacity of a disk, such mapping allows multiple logical volumesto be stored on a single physical volume, hence providing an efficientuse of the available storage media. A virtual tape server (VTS) is onedevice capable of creating and maintaining such mapping among physicalvolumes and logical volumes.

A typical VTS has a small number of physical drives that can be used forrecalling virtual volumes. The VTS has a greater number of virtualdrives or devices that provide access to the virtual volumes.

A VTS fills a physical tape by stacking multiple logical volumes. Overtime, some of these logical volumes expire and the tape contains lessactive data. Eventually the physical tape is reclaimed—a process whichreads active data from the tape. This active data is scattered on thephysical tape requiring that each logical volume be located and readfrom the tape. At the conclusion of this reclamation process the tape isnormally rewound.

Such reclamation is a time consuming process. Typically, the tape iswritten in a serpentine pattern with multiple passes. Although thelocation of each logical volume being reclaimed is known, it is aspecific location on the tape assuming the serpentine pattern wasunwound.

The motion required to read the logical volumes during the reclamationprocess can be modeled. Due to the time it takes a physical drive toreverse directions, switch from track to track and the effect of highspeed locates, the model is non-linear. As such it becomes difficult topredict a best sequence to reduce the time to access logical volumes. Intheory the most efficient method can be determined by exhaustivelyanalyzing different sequences of logical volume accesses. In practicethis is not feasible as the number of combinations to analyze isimpractical.

It would be desirable to use knowledge of the actual location of eachlogical volume on a tape based on its physical location, along withknowledge of the serpentine pattern, to increase the efficiency andreduce the overall operational time of operational requests. Suchoperational requests include the recall and reclamation operations oflogical volumes on a virtual tape server.

SUMMARY OF THE INVENTION

The present invention provides a method, system, apparatus and computerprogram product for optimizing operational requests, including recalland reclamation requests, on logical volumes in a virtual tape serverthat overcome the above-discussed shortcomings.

A method for retrieving one or more blocks of data from tape mediaincludes receiving a request to retrieve multiple groups of at least oneblock of data. The method also includes the step of retrieving a deviceblock map from a tape media which indicates the positions of the groupsof the blocks of data on the tape media and storing the device block mapin a memory location. An image of the physical layout of the requestedgroups is generated from the device block map in memory. The optimalorder of retrieval of the requested groups of data based on the physicallayout of the group in the image that minimizes the operational time ofretrieving the requested groups of data is determined. The requestedgroups of data are retrieved using the determined optimal order.

An apparatus for operating on logical volumes includes a receivingmodule configured to receive at least two operational requests, eachoperational request being directed to a logical volume stored inmountable media. The apparatus includes a storage module configured tostore each operational request for processing. An optimizer module isincluded and configured to compare the results of each operationalrequest, determine an operational request that minimizes operationaltime of carrying out the operational request and apply an optimizedoperational request to the logical volume.

An embodiment of the system to recall and reclaim logical volumes of thepresent invention includes at least one drive unit configured to receivemountable media containing at least one logical volume. The systemincludes a cache configured to store a logical volume received from themountable media and memory containing modules for execution on aprocessor. The modules include a receiving module configured to receivea plurality of operational requests, each operational request beingdirected to a logical volume stored on the mountable media and a storagemodule configured to place each operational request in storage forprocessing. An optimizer module is included and configured to apply atleast one optimization rule to at least one logical volume to minimizethe time of retrieval of one or more operational requests.

The computer program product of the present invention includes acomputer usable medium having computer usable program code forretrieving one or more blocks of data from a tape media and computerusable program code for receiving a request to retrieve multiple groupsof data blocks. The computer program product includes computer usableprogram code for retrieving a device block map from a tape mediaindicating positions of the groups of data on the tape media and storingthe device block map in a memory location. Computer usable program codefor generating from the device block map in memory an image of aphysical layout of the requested groups of data on the tape media isincluded. The computer program product includes computer usable programcode for determining the optimal order to retrieve the requested groupsof data based on the physical layout as indicated in the image in amanner that minimizes an operational time of retrieving the requestedgroups of at least one block of data. Computer usable program code isincluded for retrieving the requested groups of data from the tape mediausing the determined optimal order.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the present invention should be or are in anysingle embodiment of the invention. Rather, language referring to thefeatures and advantages is understood to mean that a specific feature,advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present invention.Accordingly, discussion of the features and advantages throughout thisspecification may, but does not necessarily, refer to the sameembodiment.

Furthermore, the described features, advantages, and characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize that theinvention may be practiced without one or more of the specific featuresor advantages of a particular embodiment. In other instances, additionalfeatures and advantages may be recognized in certain embodiments thatmay not be present in all embodiments of the invention.

Features and advantages of the present invention will become more fullyapparent from the following description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more detailed description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is a schematic block diagram illustrating one embodiment of avirtual tape system and method according to the present invention;

FIG. 2 is a schematic flow chart diagram illustrating one embodiment ofa method for optimizing operational requests in a logical volume of thepresent invention;

FIG. 3 is a graph showing the improvement in reduced processing time ofthe present invention;

FIG. 4 is a performance graph showing the relative reduction inprocessing time applying various algorithms of the present invention;and

FIG. 5 is a second performance graph showing the relative reduction inprocessing time applying various algorithms of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a schematic block diagram of one embodiment of arepresentative virtual tape system 100 for operating on logical volumes,in accordance with the present invention. The system 100 includes aprocessor controlled automated import/export module 102 which includes areceiving module and an import module (not show) for receiving andtransporting operational requests and data in virtual tape system 100.Import/export module 102 communicates with a cache manager 104 whichcommunicates with at least one direct access storage device (DASD) cache106 all controlled by a processor (not shown). The DASD cache 106temporarily stores data received through import/export module 102 andcache manager 104 and communicates with virtual or logical volumes inthe form of files, and may thus be referred to as a “cache.” Accordingto one example, the DASD cache 106 takes the form of one or more harddisk drives which may be arranged in a redundant array of independentdrives (RAID configuration), such as RAID 5. DASD cache 106 alsocommunicates with virtual tape server emulation module 108 (VTS).Virtual tape server emulation module 108 includes a group of virtualtape drives for storing, manipulating and comparing operational requestsand data processed by the present invention. Virtual tape serveremulation module 108 also processes control commands from import/exportmodule 102 and cache manager 104.

As shown in FIG. 1, virtual tape server emulation module 108 maygenerate and store the required images and maps while communicatingthrough an optimizer module 110 which includes a recall manager module112 and reclaim manager module 114. It is through optimizer module 110,recall manager module 112 and reclaim manager module 114 that thealgorithms included in the steps of the present invention are applied todetermine the optimum retrieval path and minimum operational time forcarrying out one or more operational steps including recall andreclamation operations. To carry out application of the minimumoperational time algorithm, optimizer module 110 communicates with datamover modules 116 and 118 each of which communicates with tape drives120 and 122. Data mover module 124 is included and is capable ofcommunicating directly between DASD cache 106 and tape drive 120. Thiscommunication path provides for updating of at least one tape unit withinformation received through import/export module 102 and cache manager104, and allows the virtual tape system 100 to apply a further optimizedalgorithm to identify the optimal retrieval path, which may be repeatedat any point in the data read/write process, as required by the presentinvention. It may be appreciated by those of skill in the art that datamover modules 116, 118 and 124 and tape drive 120 and 122 may includemultiple data mover modules and multiple tape drives for use in avariety of data and virtual tape systems and are not limited to thenumber illustrated in FIG. 1.

FIG. 2 illustrates a schematic flow chart diagram illustrating a methodfor optimizing operational requests and retrieval paths for logicalvolumes of the present invention as shown at 200. The optimizationprocess begins at step 202 and receives an initial list of virtualvolumes including multiple groups of one or more data blocks necessaryto process an operational request at step 204. The initial position ofthe physical tape drive 120 is identified in step 206. If the process isnot complete as shown in step 208 then a map of the virtual drive isretrieved, stored and used to generate an image of the physical layoutof the groups of data blocks. The optimal retrieval order of the datablock groups is determined by calculating the shortest retrieval timeusing one or more retrieval paths or algorithms. Each of the retrievalpaths or algorithms comprises as ordered sequence of the requested datablock groups and identifies the manner in which the tape media is to betraversed to accomplish the optimal retrieval order sequence. One suchretrieval path or algorithm is the sequence on tape (first in/first out)algorithm where the next data record in sequence is located until therequest is complete at step 210. As shown at step 212, the time tocomplete the operational request is calculated using the minimum delayto the next data record algorithm. At step 214 the time to complete therequest is calculated using the minimum reversal (the minimum tapedirection reversal sequence) algorithm. After each of these times iscalculated and stored, the times are compared and the algorithm with thelowest completion time for the operational request is chosen at step216. It may be appreciated that the sequence or order of application ofeach of the operational algorithms is not critical to the processingperformed by the present invention.

The algorithm that has the lowest minimum time to complete theoperational request is applied in step 218 and is used to process thesubset of volumes chosen in step 204 utilizing the optimal retrievalpath. This method of determining the shortest processing time deliversthe quickest completion time for the operational request made by thesystem in step 204. At step 220 it is determined if there are anyadditional or new requests made by the system and again it is determinedat step 208 if the system has completed processing the virtual volumes.If the processing is not yet complete and there are new or additionalrequests, the process again moves through steps 210, 212, 214, 216, 218and 220 to determine the which algorithm should be applied to obtain thequickest processing of the operational requests made to data on thevirtual volumes. If there are no new requests for processing at step 220then processing of the virtual volumes is completed in step 208 and theprocess ends at step 220.

Optimization algorithms are applied to the image at steps 210, 212 and214 to achieve the fastest possible processing time. Improving theefficiency of operational requests including reclamation and recall in aserpentine tape drive as disclosed herein are examples of the processcarried out by optimizer module 110 in FIG. 1 as set forth in steps 210,212 and 214 in FIG. 2 and as set forth above. Such optimization has beendetermined to be carried out utilizing one or more of the retrievalpaths based on the image of the layout of the requested data groups inmemory. One algorithm is known as sequence on tape which determines afirst in/first out sequence by moving the tape media from a currentlocation to a secondary location closest to the current location in apreferred direction and on a preferred track of said tape mediaindependent of track information. A second algorithm processes dataplaced on tape media utilizing a minimum reversal of direction of thetape media tape which moves the tape media from a current location to asecondary location closest to the current location in a preferreddirection independent of track information of the tape media. Anotheralgorithm processes data utilizing a minimum time delay to the next datasequence or element which moves the tape media from a current locationto a secondary location closest to the current location independent of adirection of movement of the tape media.

A computer program product is also presented that performs one or moreoperations to recall logical volumes from mountable media. In oneembodiment, the operations include performing the method steps outlinedabove in FIG. 2. In another embodiment of the present invention, thedefault algorithm of sequence on tape is used to provide the mostefficient processing of data. In further embodiment of the presentinvention, to improve the processing efficiency, a second algorithm iscompared to the sequence on tape processing. The second algorithm is theminimum reversal of direction of the tape media. This algorithm willmove down the tape in a given direction and select the closest logicalvolume that can be accessed in that direction from the end of the lastvolume read (or initially the beginning of the tape) without having tostop. In determining the efficiency of this algorithm, it is recognizedthat time is required to move the tape head if a different paralleltrack is chosen. When a pass is completed in that direction, the tapewill move to the first logical volume that can be read in the oppositedirection, that first volume being the one closest to the “beginning” ofa scan in the new direction. The intent of this algorithm is to takelong passes down the tape and minimize reversals of direction thusimproving processing efficiency.

A third algorithm is also used to compare the results of the first twoalgorithms to further improve processing efficiency. The third algorithmis the minimum delay to next data element or closest logical volume(CLVOL) algorithm. From a given point in tape—the end of the last volumeread (or initially the beginning of the tape)—the closest logical volumeis selected. The closest logical volume being the volume that takes theleast time to locate. Given the high speed locate functionality of thephysical drive, this volume could theoretically be further awayphysically than other volumes. This algorithm would tend to haveincreased tape reversals, but could be more efficient on clusters ofdata.

In operation, each of these algorithms is fast, since they only evaluatewhich volume should be next from a given position. Using the model, thepredicted performance of each of the sequences is calculated, includinga final move to the beginning of the tape as the tape will be unloadedas part of this operation. Once the predicted performance of all thevolumes on the tape is determined, the best algorithm (based on minimumoverall time) is chosen and applied to the operational process.

The present invention provides an efficient and simple method todetermine an improved sequence of accessing logical volumes prior toreclaiming a physical volume. Specifically, the optimization processincludes developing a model for physical tape operations, developingalgorithms as described above that suggest an access pattern andmodeling those patterns then selecting the best access pattern whichminimizes the processing time.

As discussed above, the modules for receiving a plurality of operationalrequests, placing each request in a queue for processing, reordering thequeue in accordance with at least one optimization rule, and/orretrieving requested groups of data using a determined optimal order,could be implemented by hardware, firmware, software, or the like, orany combination thereof. These and other means for receiving, queuingand optimizing operational requests could be implemented to practice theteachings of this invention.

It will be appreciated that additional optimization rules could beapplied to the processing of recall requests which could reorder therecall requests in the optimizer module 110. These and other suchoptimization rules could increase efficiency, practicality, or utilityand fall within the scope of this invention. It will further beappreciated that these and other optimization rules could be appliedsingly or in combination to practice the teachings of this invention.

The schematic flow chart diagrams included herein are generally setforth as logical flow chart diagrams. As such, the depicted order andlabeled steps are indicative of one embodiment of the presented method.Other steps and methods may be conceived that are equivalent infunction, logic, or effect to one or more steps, or portions thereof, ofthe illustrated method. Additionally, the format and symbols employedare provided to explain the logical steps of the method and areunderstood not to limit the scope of the invention. Although variousarrow types and line types may be employed in the flow chart diagrams,they are understood not to limit the scope of the corresponding method.Indeed, some arrows or other connectors may be used to indicate only thelogical flow of the method. For instance, an arrow may indicate awaiting or monitoring period of unspecified duration between enumeratedsteps of the depicted method. Additionally, the order in which aparticular method occurs may or may not strictly adhere to the order ofthe corresponding steps shown.

The results of application of the optimization algorithms of the presentinvention are shown in FIGS. 3, 4 and 5. Specifically, the graph of FIG.3 compares the results of application of the first in/first out (base)algorithm to each of the minimum reversal and closest (or next sequenceon tape) algorithms. The scattering of the results around zero indicatesthat one or the other is better for any given sample. The varyingresults at 1 percent and 2 percent active data shows that neithertechnique is always better at a given percentage active data. Thereforeselecting the most efficient algorithm from a set of modeled results isthe most appropriate technique.

It should be noted that the first in/first out (in logical order) is themost efficient solution at both 0% active data and at 100% active data.On a virtual tape server, reclaim thresholds of 10% active data aretypically used, but any value can be used, although such thresholdvalues are typically below 50%.

Referring to FIGS. 4 and 5, each algorithm was processed for variouspercent active data tapes each with a different random pattern. Theaverages of these patterns are shown. The first set is for 800 MBvolumes (full volumes on a VTS). The average of the improvement ishigher in some cases as the method selects the individual best algorithmand will therefore end up with a higher average value. This plot is inpercentage improvement in reclamation time using the closest and theminimum reversal algorithms versus the sequential or first in/first out(base) algorithm.

As shown in FIG. 4, up to 30% improvement over the sequential or firstin/first out algorithm can be achieve using the best of the closest andminimum reversal algorithms. In addition, it shows that the minimumreversal algorithm is best at low percentages and the closest algorithmis better in general. When using random volumes (100-800 MB), theimprovements obtained through the use of the present invention arefurther enhanced.

As may be appreciated, it is not feasible to calculate the absolute bestcase sequence in all cases as the value of the return begins to diminishbased on the time to process the results. Such results were calculatedfor 1% active and 2% active as shown in the graph in FIG. 3. At the lowpercent active distributions, the time to process the results and selectthe best of the algorithms is better than any single solution, and isclose to the absolute best sequence.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom very large scale integration (VLSI)circuits or gate arrays, off-the-shelf semiconductors such as logicchips, transistors, or other discrete components. A module may also beimplemented in programmable hardware devices such as field programmablegate arrays, programmable array logic, programmable logic devices or thelike.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions that may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically, comprise the module and achieve the stated purpose for themodule.

A module of executable code may be a single instruction, or manyinstructions, and may even be distributed over several different codesegments, among different programs, and across several memory devices.Similarly, operational data may be identified and illustrated hereinwithin modules, and may be embodied in any suitable form and organizedwithin any suitable type of data structure. The operational data may becollected as a single data set, or may be distributed over differentlocations including over different storage devices, and may exist, atleast partially, merely as electronic signals on a system or network.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment.

Reference to a computer program product may take any form capable ofgenerating a signal, causing a signal to be generated, or causingexecution of a program of machine-readable instructions on a digitalprocessing apparatus. A computer program product may be embodied by atransmission line, a compact disk, digital-video disk, a magnetic tape,a Bernoulli drive, a magnetic disk, a punch card, flash memory,integrated circuits, or other digital processing apparatus memorydevice.

Furthermore, the described features, structures, or characteristics ofthe invention may be combined in any suitable manner in one or moreembodiments. In the forgoing description, numerous specific details areprovided, such as examples of programming, software modules, userselections, network transactions, database queries, database structures,hardware modules, hardware circuits, hardware chips, etc., to provide athorough understanding of embodiments of the invention. One skilled inthe art will recognize, however, that the invention may be practicedwithout one or more of the specific details, or with other methods,components, materials, and so forth. In other instances, well-knownstructures, materials, or operations are not shown or described indetail to avoid obscuring aspects of the invention.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method for retrieving one or more blocks of data from a tape media,the method comprising: receiving a request to retrieve multiple groupsof at least one block of data; retrieving a device block map from a tapemedia indicating positions of the groups of at least one block of dataon the tape media and storing said device block map in a memorylocation; generating from the device block map in memory an image of aphysical layout of the requested groups of at least one block of data onthe tape media; determining an optimal order to retrieve the requestedgroups of data based on the physical layout of the requested groupsindicated in the image in a manner that minimizes an operational time ofretrieving the requested groups of at least one block of data; andretrieving the requested groups of at least one block of data from thetape media using the determined optimal order.
 2. The method of claim 1,wherein determining the optimal order further comprises: determining oneor more retrieval paths based on the image of the layout of therequested groups of the at least one block of data in memory, whereineach of the retrieval paths comprises an ordered sequence of therequested groups of the at least one block of data and the manner inwhich the tape media is to be traversed to accomplish the retrieval ofthe ordered sequence; determining a sum of operational times for each ofthe retrieval paths; selecting an optimal one of the retrieval pathsbased on the lowest sum of the operational times; and retrieving theblocks of data from the tape media using the optimal retrieval path. 3.The method of claim 2, wherein determining one or more retrieval pathsbased on the image of the layout of the requested groups of the at leastone block of data in memory includes determining a first in/first outsequence which moves the tape media from a current location to asecondary location closest to the current location in a preferreddirection and on a preferred track of said tape media.
 4. The method ofclaim 2, wherein determining one or more retrieval paths based on theimage of the layout of the requested groups of the at least one block ofdata in memory includes determining a minimum tape direction reversalsequence which moves the tape media from a current location to asecondary location closest to the current location in a preferreddirection independent of track information of the tape media.
 5. Themethod of claim 2, wherein determining one or more retrieval paths basedon the image of the layout of the requested groups of the at least oneblock of data in memory includes determining a minimum time delay tonext data sequence which moves the tape media from a current location toa secondary location closest to the current location independent of adirection of movement of the tape media.
 6. The method of claim 1,wherein the determined optimal order comprises a minimum time ofretrieval of the requested groups of at least one block of data from thetape media and said optimal order is determined after a first retrievalof at least one block of data.
 7. The method of claim 6, wherein saidoptimal order is determined after a first retrieval of at least oneblock of data and said optimal order determination is repeated afterretrieval of each at least one block of data.
 8. An apparatus foroperating on logical volumes, the apparatus comprising: a receivingmodule configured to receive at least two operational requests, eachoperational request being directed to a logical volume stored in amountable media; a storage module configured to store each operationalrequest for processing; and an optimizer module configured to comparethe results of each operational request, determine an operationalrequest that minimizes an operational time of carrying out theoperational request and applying an optimized operational request tosaid logical volume.
 9. The apparatus of claim 8, wherein one of saidoperational requests corresponding to said mountable media are groupedin said storage module according to a first in/first out sequence of atleast two operational requests on said mountable media.
 10. Theapparatus of claim 9, wherein said first in/first out sequence includesmoving the mountable media from a current location to a secondarylocation closest to the current location in a preferred direction and ona preferred track of said mountable media.
 11. The apparatus of claim 8,wherein one of said operational requests corresponding to said mountablemedia are grouped in said storage module according to a minimum tapedirection reversal sequence of at least two operational requests on saidmountable media.
 12. The apparatus of claim 11, wherein said minimumtape direction reversal sequence includes moving the mountable mediafrom a current location to a secondary location closest to the currentlocation in a preferred direction independent of track information ofsaid mountable media.
 13. The apparatus of claim 8, wherein one of saidoperational requests corresponding to said mountable media are groupedin said storage module according to a minimum time delay to next datasequence of at least two operational requests on said mountable media.14. The apparatus of claim 13, wherein said minimum time delay to nextdata sequence includes moving the mountable media from a currentlocation to a secondary location closest to the current locationindependent of direction of said mountable media.
 15. The apparatus ofclaim 8, wherein said receiving module is configured to receive and saidstorage module is configured to place and process at least two of afirst in/first out sequence, a minimum tape direction reversal sequenceand a minimum time delay to next data sequence of said at least twooperational requests on said mountable media, and said optimizer moduleis configured to reorder said storage module in accordance with anoptimization rule which chooses a sequence with a lowest time value tocompletion and applies an optimized rule that has the lowest time valueto completion to said logical volume.
 16. The apparatus of claim 15,wherein said optimizer module is configured to reorder said storagemodule in accordance with an optimization rule which chooses a sequencewith the lowest time value to completion and applies an optimizationrule that has the lowest time value to completion to said logicalvolume, wherein data is reclaimed from said mountable media and saidoptimizer module repeats the storage module reorder and optimizationsequences.
 17. A system to recall and reclaim logical volumes, thesystem comprising: at least one drive unit configured to receive amountable media containing at least one logical volume; a cacheconfigured to store a logical volume received from the mountable media;and a memory containing modules for execution on a processor, themodules comprising: a receiving module configured to receive a pluralityof operational requests, each operational request being directed to alogical volume stored on the mountable media; a storage moduleconfigured to place each operational request in storage for processing;and an optimizer module configured to apply at least one optimizationrule to minimize a time of retrieval of an operational request to saidat least one logical volume.
 18. A computer program product comprising acomputer usable medium having computer usable program code forretrieving one or more blocks of data from a tape media, said computerprogram product including: computer usable program code for receiving arequest to retrieve multiple groups of at least one block of data;computer usable program code for retrieving a device block map from atape media indicating positions of the groups of at least one block ofdata on the tape media and storing said device block map in a memorylocation; computer usable program code for generating from the deviceblock map in memory an image of a physical layout of the requestedgroups of at least one block of data on the tape media; computer usableprogram code for determining an optimal order to retrieve the requestedgroups of data based on the physical layout of the requested groupsindicated in the image in a manner that minimizes an operational time ofretrieving the requested groups of at least one block of data; andcomputer usable program code for retrieving the requested groups of atleast one block of data from the tape media using the determined optimalorder.
 19. The computer program product of claim 18, wherein thecomputer usable program code determining for an optimal order furtherincludes: computer usable program code for determining one or moreretrieval paths based on the image of the layout of the requested groupsof the at least one block of data in memory, wherein a beginning and anend location of at least two of the groups are discontinuous and each ofthe retrieval paths comprises an ordered sequence of the requestedgroups of the at least one block of data and determining the manner inwhich the tape media is to be traversed to accomplish the retrieval ofthe ordered sequence; computer usable program code for determining a sumof times for each of the retrieval paths; computer usable program codefor selecting an optimal one of the retrieval paths based on the lowestdetermined sum of times; and computer usable program code for retrievingthe blocks of data from the tape media using the optimal retrieval path.20. The computer program product of claim 20, wherein the computerusable program code for determining one or more retrieval paths based onthe image of the layout of the requested groups of the at least oneblock of data in memory includes: computer usable program code fordetermining a first in/first out retrieval path which moves the tapemedia from a current location to a secondary location closest to thecurrent location in a preferred direction and on a preferred track ofsaid tape media; computer usable program code for determining a minimumtape direction reversal retrieval path which moves the tape media from acurrent location to a secondary location closest to the current locationin a preferred direction independent of track information of the tapemedia; and computer usable program code for determining a minimum timedelay to next data retrieval path which moves the tape media from acurrent location to a secondary location closest to the current locationindependent of a direction of movement of the tape media.